Magnetic compass corrective device



Sept. 18, 1934. J 1 HAND MAGNETIC COMPASS CORRECTIVE DEVICE OriginalFiled May 31 lllllfl v!!!!!!! .J

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Patented Sept. 18, 1934 Mserrsrrc ooinrsss oonieso'rrvs .lchn Lil. Hand,Bala-Cynwyd, Pa.

DEVICE Applicationll/iay 31, 1929, Serial No. 267,212

Renewed dune 29, 1933 11 Claims.

My invention relates to a device for correcting the field of the carrierof a compass so that the compass will indicate correctly irrespectiveof.

variation in the direction of alinement of its carrier.

A purpose of my invention is to provide novel means for easilyneutralising the magnetic field of the carrier of a compass at compass,the compass being fixed to the carrie which may be a an aircraft or avehicle.

A further purpose is to adjust the field at a compass from opposing anda n n magnets by means of angular adjust: an armature of one of ma netsor by ...ieans of angular adjustments of arinatures of both the inag-.

nets, either or both according to circumstance.

A further purpose is to adjust th magnetic effect upon a compass ofalined, stationary and opposing magnets by relatively reverseangularadjustments of armature members at the respective magnets.

A further purpose is to mount two relatively perpendicular sets ofstationary opposing substantially symmetrical with respect to an axisthrough a compass, and to adjust the magnetic eilects thereof at thecompass by means of revelsely, angularly adjustable armature members. Ipreferably make each set of magnets comprise two alined, opposing andequal pa'rs of magnets, and pivotally mount an armature member angularlyadjustable wi'tl'i respec to ment or an armature of one of the pairs isaccompan ed by a corresponding reverse adjustrnent or" the armature ofthe other pair or the set.

Whether a single roagnetor a pair be used at each or" the four positionsshown, and Whether or inagnetsbe varied in strength directly at twopositions only or at all four positions, a further purpose is toneutralize the strength of the magnet or magnets initially by use of anarmature which generally parallels the magnet length and to vary themagnet strength by turning the arinatures to positions of varying angulaity to the magnet lengths.

Furth r purposes will appear in the specifiers-- tion and in the claims.

I-have elected to show one main form only of each pair, providingconnections whereby adjust-' cation and have selected a form and 1nodi-,

taken upon line 1+1 of;

Figure 2 is a broken front elevation of the structureshown in Figure 1,a cover of the corrective device being shown,

Figures 3 and a are sections of Figure 1 taken upon the lines 3-3 andi-4 thereof.

Figures 5, Sand 6a are views generally similar to Figure 1 but showingsomewhat different forms.

which the resultant of the earths magnetic fieldand a magnetic field dueto, magnetic material in the carrier.

The field due. to the magnetic material in the carrieris directionallyvariant according to variations in the angular alinement of the carrierwith respect to the magnetic meridian and must, therefore, beneutralized at the compass to avoid errors. in the readings of thecompass that will be variant with the changes in directional alinemeritsof the carrier.

The). usual way of neutralizing the magnetic fieldofa carrier at thecompass is to neutralize the east and west component of the field of thecarrier. by magnetic adjustments until the compass reads right when thecarrier alinement is in one direction and then to change the alinemeritof the carrier ninety degrees and to neutralize the new east andwest'coinponent of the carrierfield by other magnetic adjustments until.the compass again reads right.

Each neutralization of the east and west component of. the carrier fieldinvolves an adjustment bringing the magnetic field at the compass inaccord with the magnetic meridian so that the compass reads correctly,and theltwo adjustments must be on different magnetic sets that are magneti'cally' independent of one another. r If the sets are notmagnetically independen the operations must be repeated until thec0mpass reads substantially right'irrespective of the carrieralinernent, as indicated by, its reading right for two relativelyperpendicular alinernents. 1=.L'.y invention is directed towardprovidinggan effective and convenient device for operating in this samegeneral way, and in which the two magnetic adjustment sets arerelatively independentt'o a high degree.

I mount two sets of magnetic adjusters 10 and 11 respectively, sheets'lzand 13.

Each adjuster set comprises a fixed magnet member 14 alined with asimilarly fixed and substantially equivalent magnet member 15 andcooperating armature members 16 and 17 one for each magnet member, themagnet members of the two sets being in relatively perpendicularalinements. Though obviously magnets can be used as armatures, the mostsatisfactory armatures are made of magnetically permeable materialforexample soft ironwhich is not magnetized except as it receives magneticinduction from the magnets with which it cooperates.

I preferably make each magnet member comprise two magnets side by sideand on opposite sides of the pivot of the armature as illustrated inFigures 1 to 4 but optionally may make each magnet member include asingle magnet as shown in Figure 5.

In Figures 1 to 4 the magnet members comprise a pair of magnets 14 and apair of magnets 15 alined with the pair 14..

The armatures are pivotally mounted at 18 midway between the magnets oftheir respective pairs and extend transversely across the pairs ofmagnets in angularly variant positions;

They are operatively connected together by a suitable link 19 to moveequal angular distances in angularly reverse directions.

The angular adjustment of the armatures may 1 be obtained by any one ofmany different arrangements. In the illustration one of the ar-- maturesof each set, 17 carries a toothed sector 20 which meshes with a slidablerack member 22.

The rack member 22 is slidably mounted in bearings 23 and 24 and isprovided with an adjustment nut 25 outside of a flange portion 26 of oneof the discs. 7 l

The armature 16 mounted across the other pair of magnets isspring-pressed in the direction of I the arrow by a spiral spring 27 ofthe magnetic material.

One end of this spring is connected at 28 to the armature and the otherat 29 is anchored to the supporting disc.

This arrangement avoids any lost motionas I the spring tends to rotatethe members in the direction of the arrows and this rotation is stoppedby the engagement between the nut 25 and the outer edges of itssupporting bearing Desirably the upper portion of each of the rackmembers may be provided with a scale 31,

v the disc 13, and the pivot members 34 and 35 rigidly carry thearmatures 16 and 1'7 respectively at their upper ends and at their lowerends respectively carry one of the toothed sections '20. and connectionwith one of the spiral springs 27..

The disc members are flanged in the direction of their common axis at26. 1

The discs are held together by suitable screws 36 and a cover'plate'3'7slotted to pass the'nuts' fastens the device to the bottomsor topportion of a compass member 38' by screws 39. i

The effect of angular adjustment of the armatures of each set is tochange the: magnetic field from the magnets at'the compass, theeffe'ctbeing a progressive one having a magnitudedependent upon the extent ofthe angular deflection of the armatures from their transverse position.

When the armatures are squarely across the magnets as indicated in fullline position (Figure 1) the opposing pairs of magnets substantiallyneutralize one another and are without any substantial effect upon thefield at the compass.

As the armature members are moved toward the position shown in dot anddash, the magnetic effect of the set of magnets becomes graduallymaterial, progressively increasing, and the progressively increasingeffect does not appear to be materially influenced by, or to itselfmaterially affect any magnetic held of the other set, the two sets thusbeing highly independent of one another, which is an essential conditionfor effective and easy correction of the field at the compass.

In Figure 5 I show the armature members indivi'dually adjustable.Normally the armatures 17' are initially set at right angles to theirmagnets 15' and the armatures 16 then adjusted and set to a positionsuch that the opposing alined magnets 14' and 15 substantiallyneutralize one another at the compass. When subsequently adjusting thefield from either set at the compass only one of the armatures of theset need be adjusted, normally the armature 17 of either pair.

I prefer to adjust both armatures of one set simultaneously in reversedirections as illustrated in Figure l in that the field at the compassfrom either set of alined opposing magnets is then most perfectlyunaifected by the adjustment of the other set, but optionally may adjustonly one of these armatures, as illustrated in Figure 5.

The operation is generally similar to that of the prior art, the carrierbeing alined north and south and one of the sets being adjusted byscrewing the nut 25 until the compass reads correctly.

The carrier is then alined east and west and corresponding adjustment ismade at the other nut until the compass again reads correctly afterwhich the field of the carrier at the compass should be substantiallyneutral and the compass read correctly irrespective of variation indirection of alinement of the carrier.

In order to show that the armature used need not be normally tranverseto the lengths of the magnets I have shown the armatures 16 17 inFigures 6 and So, as parallel with the lengths of the single magnets14', 15', or with the lengths of the pairs'of magnets 14 15 Though Iprefer to adjust the magnetic field directly at each of the fourpositions as provided for, for example, by means of the coupling ofopposite armatures through the connections 19, because by this means Iget the double strength due to the change of magnetic flux at oppositesides of the center, I recognize that one of these opposite magnets, orpairs of magnets, if adjusted will tend to correct the field to theextent of its strength even though the other magnet or pair of magnetsacross the center be not directly corrected; and that the.

correction of one magnet, or pair of magnets, on one side of the center,even though the opposite magnet or pair be not corrected, will reactupon this opposite magnet or pair to produce a change in it.

In order to illustrate this I have shown correction or modification ofthe magnetic strength in two positions only of the four, providing forcorrection of the fixed pair of magnets 14 and 15 by movable armatures17 but not providing for correction of the magnets 14 15 whose armatures16 and 17 are fixed in such position as to permit the system to beadjusted to a zero condition of external field.

The same form of adjustment is shown conventionally in this figure andin Figure Set as in Figure 5.

In Figure 6a a single magnet only is used in 7 each of the fourpositions and each of the four armatures is made adjustable from twoadjustment positions parallel to the magnets by connections 19corresponding generally to the construction in Figure 1. There is onedifference, however, in that the positions of the two armatures make itdesirable to turn them through outriggers so of any suitable material.

The operation of the structure in Figures 6 and 6a is substantially thesame as that in the other figures.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such in so far as they fall within the reasonable spirit and scopeof my invention.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

l. A corrective set comprising two stationary alined opposing magnets,an armature pivotally mounted at each magnet and m ans forsimultaneously and reversely adjusting the angular positions of thearmatures with respect to the magnets.

2. A corrective set for neutralizing the magnetic field of a compass atthe compass, which comprises two stationary aligned opposing magnets onopposite sides angularly of the compass axis, an armature pivotallymounted at each magnet, two stationary aligned opposing magnets also onopposite sides angularly of the compass axis and located in positions 90distant respectively from the other magnets so that the four magnetsoccupy positions 90 apart about the axis, armatures mounted at therespective magnets, one for each magnet, means for simultaneouslyadjusting the angular positions of the armatures for the first magnetsand means for simultaneously adjusting the angular positions of thearmatures of the second magnets with respect to the magnets.

3. A corrective device comprising stationary alined and opposing pairsof magnets, two pivotally mounted armatures, one mounted at each pair,and connections for making relatively reverse angular adjustments in thepositions or" the armatures with respect to their adjacent magnets inorder to vary the magnetic effect from the two pairs at a point distantfrom the pairs.

4. A mounting and two relatively perpendicular magnetic corrective setsthereon, each set comprising two stationary opposing and alined pairs ofmagnets, two armatures pivotally mounted between the respective magnetsof each pair and connections for giving an angular adjustment of onearmature with a corresponding reverse angular adjustment of the other,said angular adjustments being with respect to the respectively adjacentpairs of magnets.

5. A corrective set comprising two stationary alined opposing magnets,an armature pivotally mounted at each magnet and means for adjusting theangular position of one of the armatures with respect to its adjacentmagnet.

6. A corrective set comprising two stationary alined opposing magnets,two other stationary alined opposing magnets having an alinementsubstantially perpendicular to the alinement of the first magnets, anarmature pivotally mounted at each of the magnets, means for adjustingthe angular positions of the armatures adjacent the first two magnetswith respect to the adjacent magnets and other means for adjusting theangular positions of the armatures of the two other magnets with respectto the said two other magnets.

7. A corrective set comprising two stationary alined opposing magnets,two other stationary alined opposing magnets having an alinementsubstantially at right angles to the alinement of the first magnets, anarmature pivotally mounted at each magnet and individual adjustments forindividually adjusting the angular positions of the different armatureswith respect to the adjacent magnets.

8. A corrective set for a magnetic compass, comprising two stationaryalined opposing magnets on opposite sides of the compass axis, a pivotedarmature for one of the magnets and means for adjusting the angularposition of the armature with respect to the magnets.

9. In a corrective set for a magnetic compass, two alined pairs ofstationary opposing magnets located on opposite sides of the axis of thecompass, a pivoted armature for one pair of the magnets pivoted betweenthem and adapted with movement to vary the relative strength or theadjoining poles of this pair and means for turning the armature.

10. A corrective set comprising two alined pairs of stationary opposingmagnets, two other alined pairs of stationary opposing magnets having analinement substantially perpendicular to the alinement of the first twopairs, an armature pivotally mounted at one of the pairs, a secondarmature mounted at one of the adjoining pairs, means for adjusting theangular position of the first named armature with respect to the saidone pair and separate means for adjusting the angular position of thesecond named armature with respect to the said adjoining pair.

11. A corrective set comprising individual alined opposing magnetsspaced 90 apart about a circle, an armature mounted at each magnet,means for adjusting the relative position of one or" the armatureswhereby the armature'directly opposite is automatically adjusted andmeans for angularly adjusting the relative position of the armatureadjoining the first named armature whereby the armature directlyopposite thereto is automatically adjusted, said angular adjustmentsbeing with respect to the magnets.

JOHN L. H. HAND.

